Ion implantation is a process by which dopants or impurities are introduced into a substrate via bombardment. In semiconductor manufacturing, the dopants are introduced to alter electrical, optical, or mechanical property. For example, dopants may be introduced into an intrinsic semiconductor substrate to alter the type and level of conductivity of the substrate. In manufacturing an integrated circuit (IC), a precise doping profile is often important for proper IC performance. To achieve a desired doping profile, one or more dopants may be implanted in the form of ions in various doses and various energy levels.
In some implementations, a plasma is created in an ion source chamber. This plasma contains positively charged dopant ions. An extraction electrode assembly may be disposed outside of and proximate the ion source chamber. This extraction electrode assembly may include at least a suppression electrode and a ground electrode. Each of the electrodes in the extraction electrode assembly may have an aperture, through which the positively charged dopant ions may pass. In addition, one or more of the electrodes may be negatively biased to attract the positively charged dopant ions through an extraction aperture in the ion source chamber and through the apertures in the extraction electrode assembly. These extracted dopant ions form an ion beam, which is then used to implant the substrate.
One cause of ion source failure is accumulation of materials on the inner wall of the ion source chamber, the suppression electrode and the ground electrode. In addition, the materials may accumulate on the apertures. If formed on the inner wall of the ion source chamber, the materials may reduce the rate by which ions are generated and reduce the beam current.
One way to prevent the effect of the material accumulation is to intermittently replace the ion source with a clean ion source. Alternatively, the ion source may have to be manually cleaned after powering down the entire ion source and after releasing the vacuum. However, these measures require the ion source or the entire ion implanter system to be powered down and to release the vacuum within the system. Moreover, the ion implanter system, after replacing or cleaning the ion source, must be powered and evacuated to reach operational condition. Accordingly, these maintenance processes may be very time consuming. In addition, the ion implanter system is not used during the maintenance processes. As such, frequent maintenance processes may decrease IC production time, while increasing its manufacturing cost and placing excessive financial burden on the manufacturers and, ultimately, the consumers. In view of the foregoing, it would be desirable to provide a new technique for improving the performance and extending the lifetime of an ion source to overcome the above-described inadequacies and shortcomings.